Many different types of materials including fabric, paper, films, foils, and the like are formed into what is commonly known as a web. In the production, processing, or treatment of a web, the web is often moving as it progresses from one operation, such as cutting, slitting, printing, and the like, to the next operation. It is important to be able to accurately determine the position of the web as it moves so that it can be properly aligned for the various operations.
One commonly known technique for determining the position of a moving web involves detecting the position of the physical edge of the web using an ultrasonic edge detector. Another commonly known technique for determining the position of a moving web involves detecting the position of the physical edge of the web using a light-based edge detector. Despite the advantages of these types of detectors, there are shortcomings associated with both of them. Ultrasonic detectors are only effective for determining the position of certain types of materials. While ultrasonic detectors work well with many types of materials, and in particular, materials that are transparent or translucent such as thin paper sheets or transparent plastic, they do not work well with other materials, such as non-woven fabric and mesh. Similarly, while light-based detectors work well with certain types of materials, they do not work well with other types of materials, mainly those that are transparent or translucent. Thus, each of the ultrasonic and light based detectors works well with some types of materials, but neither works well with all types of materials.
In addition, the determination of which detector type is best suited for a given application is made by a person whose decision may or may not be based upon the actual performance of the different types of detectors and whose decision may or may not result in the selection of the optimum detector for a given application.
Further, in order to switch from one type of detector to another, a person is required to physically remove the existing detectors and replace them with another type of detector. This process is time consuming and labor intensive.
A system and method for determining the position of an edge of a web that overcome these deficiencies are needed.